Solar collector and solar heating system using same

ABSTRACT

A solar collector includes a substrate having a top surface and a bottom surface opposite to the upper surface, a sidewall, a transparent cover, and a heat-absorbing layer. The sidewall is arranged on the periphery of the top surface of the substrate. Thea transparent cover is disposed on the sidewall opposite to the substrate to form a sealed chamber with the substrate together. The heat-absorbing layer is disposed on the upper surface of the substrate and includes a carbon nanotube film having a plurality of carbon nanotubes. The carbon nanotubes in the carbon nanotube film are aligned along a same direction or along different directions.

This application is related to applications entitled, “SOLAR COLLECTORAND SOLAR HEATING SYSTEM USING SAME”, filed Mar. 12, 2009, 12/381,577;“SOLAR COLLECTOR AND SOLAR HEATING SYSTEM USING SAME”, filed Mar. 12,2009, 12/381,611 “SOLAR COLLECTOR AND SOLAR HEATING SYSTEM USING SAME”,filed Mar. 12, 2009, 12/381,578; AND “SOLAR COLLECTOR AND SOLAR HEATINGSYSTEM USING SAME”, filed Mar. 12, 2009, 12/381.551. The disclosures ofthe above-identified applications are incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a solar collector and, particularly,to a solar collector incorporating carbon nanotubes.

2. Description of Related Art

Generally, solar collectors can be divided into two typical types: pipesolar collectors and flat plate solar collectors. For many applications,it has been demonstrated that the most efficient and least expensivetype of solar collector is the flat plate collector. Referring to FIG.4, a typical flat plate collector 500, according to the prior art,includes a substrate 52, a sidewall 56 arranged on the periphery of thesubstrate 52, and a transparent cover 50 fixed on the sidewall 56opposite to the substrate 52. A sealed chamber 60 is formed between thesubstrate 52 and the transparent cover 50. A number of supporters 58 aredispersed in the sealed chamber 60 at random. The transparent cover 50is used for passage of light and is made of glass, plastic and othertransparent materials. The substrate 52 is made of absorbing materials,such as copper, aluminum, or the likes. In use, the light enters thecollector 500 through the cover 50, and is absorbed by the substrate 52.Thus, heat is generated by the substrate 52 and is transferred to astorage apparatus (not shown).

It is understood that the substrate 52 must be kept from oxidizing tomake sure that the collector 500 has high efficiency. When making thesubstrate 52 of the collector 500, a high vacuum surrounding is neededto prevent oxidation of the collector 500. Further, the absorbingefficiency of the substrate 52 is limited by the material used.Therefore, the efficiency of the collector 500 is limited.

What is needed, therefore, is to provide a solar collector and a solarheating system using the solar collector that can help overcome theabove-described shortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present solar collector and solar heating system canbe better understood with references to the following drawings. Thecomponents in the drawings are not necessarily drawn to scale, theemphasis instead being placed upon clearly illustrating the principlesof the present solar collector.

FIG. 1 is a schematic, side view of a solar heating system having acarbon nanotube film in accordance with the present embodiment.

FIG. 2 is a schematic, top view of a solar heating system of FIG. 1.

FIG. 3 is a Scanning Electron Microscope (SEM) image of a carbonnanotube film of a carbon nanotube including a plurality of carbonnanotubes arranged along different directions.

FIG. 4 is a schematic view of a typical solar collector, according tothe prior art.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate at least one embodiment of the solar collector, in at leastone form, and such exemplifications are not to be construed as limitingthe scope of the invention in any manner.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

References will now be made to the drawings to describe, in detail,embodiments of the solar collector.

Referring to FIGS. 1-2, a solar heating system 100 according to a firstembodiment is shown. The solar heating system 100 includes a solarcollector 10 and a storage apparatus 20 connected to the solar collector10. The storage apparatus 20 is configured for storing heat generated bythe solar collector 10.

The solar collector 10 includes a substrate 11, a sidewall 12, atransparent cover 13, a heat-absorbing layer 14 and a number ofsupporters 15. The substrate 11 has a top surface 111 and a bottomsurface 112 opposite to the top surface 111. The transparent cover 13has a bottom surface 131. The sidewall 12 is mounted on the periphery ofthe top surface 111 of the substrate 11. The transparent cover 13 isattached on the sidewall 12 opposite to the substrate 11 to form asealed chamber 16 in cooperation with the sidewall 12 and the substrate11. The heat-absorbing layer 14 is disposed on the top surface 111 ofthe substrate 11 and received in the sealed chamber 16.

The material of the substrate 11 can be selected from one ofheat-conducting materials, such as metal, glass, polymer, and so on. Athickness of the substrate 11 can be in a range from about 100 μm toabout 5 mm. The shape of the substrate 11 is not limited and may betriangular, hexagonal, and so on.

The transparent cover 13 may be a solar radiation access window. Thematerial of the transparent cover 13 can be selected from a groupconsisting of glass, plastic, transparent porcelain, polymer and othertransparent materials. A thickness of the transparent cover 13 can be ina range from about 100 μm to about 5 mm. The shape of the transparentcover 13 is not limited, and may be triangle, hexagon, quadrangle, andso on.

The sidewall 12 is configured for supporting the transparent cover 13,and then formed the sealed chamber 16 between the transparent cover 13and the substrate 11. The sidewall 12 is made of materials selected fromglass, plastics, polymers, and the like. A height of the sidewall 12 isnot limited. A thickness of the sidewall 12 can be in a range from about100 μm to about 500 μm. In the present embodiment, the range is 150 μmto 250 μm.

The sealed chamber 16 may be a vacuum chamber or an atmospheric chamberfilled with thermal-insulating materials. In the present embodiment, thesealed chamber 16 is an atmospheric chamber, and the thermal-insulatingmaterials filled therein can be transparent and/or translucentmaterials, such as transparent foam rubber, transparent foam plastics,or the like. The sealed chamber 16 can also be filled withthermal-insulating gas, such as nitrogen, and/or inert gases.

The heat-absorbing layer 14 includes a carbon nanotube film comprised ofcarbon nanotubes. The carbon nanotubes in the carbon nanotube film arearranged along a same direction or arranged along different directions.The carbon nanotubes in the carbon nanotube film can rest upon eachother. Adjacent carbon nanotubes are attracted to each other andcombined by van der Waals attractive force. There is an angle existbetween each carbon nanotube of the carbon nanotube film and a surfaceof the carbon nanotube film, and the angle ranges from about 0 degreesto about 15 degrees. In one embodiment, when the carbon nanotubes in thecarbon nanotube film are arranged along different directions, the carbonnanotube film can be isotropic. The carbon nanotubes can be selectedfrom a group consisting of the single-walled carbon nanotubes,double-walled carbon nanotubes, and combinations thereof. A diameter ofthe single-walled carbon nanotube is in a range from about 0.5 nm toabout 50 nm. A diameter of the double-walled carbon nanotube is in therange from about 1 nm to about 50 nm. A length of the carbon nanotubesis longer than 10 μm. In the present embodiment, the length is rangedfrom about 100 μm to about 1 mm. A thickness of the carbon nanotube filmis ranged from about 0.5 nm to about 1 mm.

The carbon nanotube film can be formed by pressing a carbon nanotubearray. The angle is closely related to pressure applied to the carbonnanotube array. The greater the pressure, the smaller the angle. It isto be understood that the shape of the pressure head used to apply apressure and the pressing direction can determine the direction of thecarbon nanotubes arranged the carbon nanotube film. When a pressure head(e.g a roller) is used to travel across and press the array of carbonnanotubes along a predetermined single direction, a carbon nanotube filmhaving a plurality of carbon nanotubes primarily aligned along a samedirection is obtained. In FIG. 3, when the pressure head is used totravel across and press the array of carbon nanotubes severaldirections, variation will occur in the orientation of the nanotubes.Variations in pressure can also achieve different angles between thecarbon nanotubes and the surface of the carbon nanotube film.

The supporters 15 are configured for increasing the strength of thesolar collector 10. The supporters 15 are dispersed in the sealedchamber 16 at random or in a desired pattern. The supporters 15 arespaced from each other and disposed between the substrate 11 and thetransparent cover 13. The supporters 15 can be made ofthermal-insulating materials, such as glass, plastics, rubber, and soon. A height of the supporters 15 is the same as that of the sidewall 12for contacting with the transparent cover 13. The shape of thesupporters 15 is not limited, and may be, for example, rounded orbar-shaped.

The solar collector 10 further includes a reflection layer 17. Thereflection layer 17 is disposed on the bottom surface 131 of thetransparent cover 13. The reflection layer 17 is configured for allowingthe visible light and near infrared light of the sunlight passingthrough the transparent cover 13 and reflecting the far infrared lightradiated from the heat-absorbing layer 14 to prevent thermal radiationfrom escaping the sealed chamber 16 having a trapping effect. Thus, thelight absorbing efficiency of the solar collector 10 is improved. Thereflection layer 17 may be an indium tin oxide (ITO) film or a titaniumdioxide film and a thickness of the reflection layer 17 ranges fromabout 10 nm to about 1 μm.

The storage apparatus 20 is located on a bottom surface 112 of thesubstrate 11 and may include a number of pipes (not shown) filled withcirculating fluid. The fluid may be selected from the group of water,glycol, or the like.

In use, since the carbon nanotube film is black and has a capability ofabsorbing most heat of the solar spectrum. The sunlight travels throughthe transparent cover 13 and reaches the heat-absorbing layer 14. A goodportion of the radiation of the sunlight is absorbed by theheat-absorbing layer 14. Then, the heat absorbed by the heat-absorbinglayer 14 is conducted to the storage apparatus 20 via the substrate 11.Therefore, the solar collector 10 has a high efficiency because of theexcellent light absorbing and heat transferring properties of the carbonnanotubes of the heat-absorbing layer 14. The solar collector 10 isdurable due to the toughness of the carbon nanotubes in the carbonnanotube film. The use of carbon nanotube, which does not oxidizeeasily, eliminated the need for a high vacuum. This significantlyreduces the cost of the solar collector 10.

Finally, it is to be understood that the above-described embodiments areintended to illustrate rather than limit the invention. Variations maybe made to the embodiments without departing from the spirit of theinvention as claimed. The above-described embodiments illustrate thescope of the invention but do not restrict the scope of the invention.

What is claimed is:
 1. A solar collector comprising: a substrate; asidewall; a transparent cover, wherein the substrate, the sidewall andthe transparent cover form a sealed chamber; a reflection layer disposedon a surface of the transparent cover, the reflection layer is locatedin the sealed chamber; and a heat-absorbing layer disposed between thesubstrate and the reflection layer, the heat-absorbing layer comprisinga carbon nanotube film comprising a plurality of carbon nanotubes,wherein an angle between a primary alignment direction of the carbonnanotubes and a surface of the carbon nanotube film is in a range of 0degrees to 15 degrees, wherein the reflection layer is directly oppositeto the heat-absorbing layer.
 2. The solar collector as claimed in claim1, wherein a thickness of the reflection layer is in a range from 10nmto 1 μm.
 3. The solar collector as claimed in claim 1, wherein thereflection layer comprises an indium tin oxide or a titanium dioxide. 4.A solar-heating system comprising: a solar collector comprising: asubstrate; a sidewall; a transparent cover, wherein the substrate, thesidewall and the transparent cover form a sealed chamber, wherein thesealed chamber is an atmospheric chamber having a pressure equal to anatmospheric pressure; and a heat-absorbing layer disposed between thesubstrate and the transparent cover, the heat-absorbing layer comprisinga carbon nanotube film comprising a plurality of carbon nanotubes,wherein an angle between a primary alignment direction of the carbonnanotubes and a surface of the carbon nanotube film is in a range of 0degrees to 15 degrees; a reflection layer located on the bottom surfaceof the transparent cover and being directly opposite to theheat-absorbing layer; and a heat storage apparatus connected to thesubstrate and configured for storing heat generated by theheat-absorbing layer.
 5. The solar collector as claimed in claim 1,further comprising a plurality of supporters located in the sealedchamber, wherein each of the plurality of supporters contacts with thereflection layer and the heat-absorbing layer.
 6. The solar collector asclaimed in claim 1, wherein the plurality of carbon nanotubes arearranged along a same direction.
 7. The solar collector as claimed inclaim 1, wherein the plurality of carbon nanotubes are arranged alongdifferent directions.
 8. The solar collector as claimed in claim 1,wherein the plurality of carbon nanotubes are combined together andattracted to each other by van der Waals attractive force.
 9. The solarcollector as claimed in claim 1, wherein a thickness of the carbonnanotube film is in a range from 0.5 nm to 1 mm.
 10. The solar heatingsystem as claimed in claim 4, further comprising a plurality ofsupporters located between the substrate and the transparent cover. 11.The solar-heating system as claimed in claim 4, wherein the atmosphericchamber is filled with thermally-insulating materials.
 12. Thesolar-heating system as claimed in claim 11, wherein thethermally-insulating materials are transparent foam rubber ortransparent foam plastic.
 13. The solar-heating system as claimed inclaim 4, wherein the heat absorbed by the heat-absorbing layer isconducted to the storage apparatus via the substrate.
 14. Thesolar-heating system as claimed in claim 4, wherein the carbon nanotubefilm consists of the plurality of carbon nanotubes.
 15. The solarcollector as claimed in claim 1, wherein the sealed chamber is anatmospheric chamber having a pressure equal to an atmospheric pressure.16. The solar collector as claimed in claim 1, wherein the carbonnanotube film consists of the plurality of carbon nanotubes.